Propagating light to be sensed

ABSTRACT

Light to be sensed is spreaded across an entry surface of a transmission structure with a laterally varying energy transmission function. For example, the light could be output from a stimulus-wavelength converter, provided through an optical fiber, or it could come from a point-like source or broad area source. Output photons from the transmission structure can be photosensed by photosensing components such as an array, position sensor, or array of position sensors. Wavelength information from the light can be obtained in response to the photosensing component. Spreading can be performed by air, gas, transparent material, or vacuum in a gap, by a region or other part of a lens, or by an optical fiber end surface. If the light comes from more than one source, a propagation component can both spread the light and also keep light from the sources separate.

The present application is related to the following co-pendingapplications, each of which is hereby incorporated by reference in itsentirety: “Chip-Size Wavelength Detector”, U.S. patent application Ser.No. 10/922,870; “Biosensor Using Microdisk Laser”, U.S. patentapplication Ser. No. 10/930,758; “Anti-resonant Waveguide Sensors”, U.S.patent application Ser. No. 10/976,434; “Photosensing Throughout EnergyRange and in Subranges”, U.S. patent application Ser. No. 11/______[Attorney Docket No. 20040195Q-US-NP/U1047/024]; “Sensing PhotonEnergies of Optical Signals”, U.S. patent application Ser. No. 11/______[Attorney Docket No. 20042101-US-NP/U1047/025]; “Sensing Photon EnergiesEmanating From Channels or Moving Objects”, U.S. patent application Ser.No. 11/______ [Attorney Docket No. 20050125-US-NP/U1047/026]; “ProvidingLight To Channels Or Portions”, U.S. patent application Ser. No.11/______ [Attorney Docket No. 20051553-US-NP/U1047/027]; “SensingPhoton Energies Emanating from Channels”, U.S. patent application No.11/______ [Attorney Docket No. 20042101Q-US-NP/U1047/030; “TransmittingLight With Photon Energy Information”, U.S. patent application Ser. No.11/______ [Attorney Docket No. 20041526-US-NP/U1047/021]; and “ObtainingAnalyte Information”, U.S. patent application Ser. No. 11/______[Attorney Docket No. 20041527-US-NP/U1047/022].

BACKGROUND OF THE INVENTION

The present invention relates generally to propagation of light, andmore particularly to propagation of light that is to be sensed.

Fuhr, P. L., “Measuring with Light”, Sensors Magazine Online, May 2000,pp. 1-11, available at www.sensorsmag.com/articles/0500/26/, describessensors that are sometimes referred to as fiber-optic sensors.Fiber-optic sensors have advantages over conventional electrical- andelectromechanical-based sensors, stemming mainly from the fact that thefibers are made of nonconducting glass and photons, not electrons, arethe signal propagation elements; as a result, the sensors are immune toelectromagnetic interference (EMI) and can operate in harshenvironmental conditions, offering a geometric versatility that allowsunobtrusive sensing. More than 60 different parameters can be measuredusing fiber-optic sensors. In extrinsic fiber-optic sensors, the opticalfiber acts as a transmit/receive light conduit, with signal modulationoccurring outside of the fiber, such as in a modulation region thatreceives light of known parametric values and provides light with achanged characteristic. In intrinsic fiber-optic sensors, on the otherhand, an external perturbation directly interacts with the optical fiberand modulates the light signal in the fiber, such as by changing theoptical fiber's waveguide controlling boundary conditions.

Various types of optic-fiber sensors as described by Fuhr have beendeveloped. Many fiber-optic sensors are based on Fiber Bragg Gratings(FBGs), which can be fabricated by exposing a photosensitive opticalfiber to a periodic pattern of strong ultraviolet light or by etching aperiodic pattern directly into the core of the fiber, forming a periodicmodulation of the refractive index along the core. Plastic opticalfibers (POF) have been applied to sensing in the form of diffractingstructures in single- and multi-mode POF with various fabricationtechniques. Photonic crystal sensors are the two- and three-dimensionalanalogs to FBGs, with a periodic modulation of the refractive index inall directions resulting in special reflection and transmissionproperties. In addition to other applications, various fiber-opticsensors and other optical sensors have been proposed for use inbiosensing.

In fiber-optic sensors that indicate stimulus change in the form ofwavelength shift in output light, additional systems have been developedfor detecting the wavelength shift. Some examples include a broadbandlight source in combination with a spectrum analyzer and, alternatively,a tunable laser with a narrow line width, sweeping periodically acrossthe reflectivity peak or resonance dip of the sensor cavity.

Othonos, A., and Kalli, K., Fiber Bragg Gratings, Artech HousePublishers, Boston, 1999, pp. 304-330, provide an overview of readouttechniques for FBGs.

U.S. Pat. No. 6,785,002 describes a variable filter-based opticalspectrometer that uses a tapered Fabry-Perot type linear variableoptical filter in conjunction with an optical detector array. The inputsignal is typically carried on an optical fiber and lenses are used toexpand and deliver the essentially point source of light from a fiberend into an optical beam that illuminates the variable filter.

U.S. Pat. No. 5,166,755 describes a spectrometer apparatus in which aspectrum resolving sensor contains an opto-electronic monolithic arrayof photosensitive elements and a continuous variable optical filter. Thefilter can include a variable thickness coating formed into a wedgeshape on a substrate or directly on the surface of the array. Ifpolychromatic light passes through the variable filter and is spectrallyresolved before incidence on the array, the output of all the elementsin the array provides the spectral contents of the polychromatic light.High spectral resolving power is obtained by subtracting the outputsignals of adjacent elements in the array. Non-imaging applicationsinclude measurement of spectral transmission through samples; formolecular absorption and emission spectra; for spectral reflectancemeasurements; for pollution and emission control by measuringtransmission or absorption; for astronomical spectral analyses ofstellar radiation; for pyrometry by measuring thermal radiation; andunderwater spectrometry.

It would be advantageous to have improved techniques for structures thatpropagate light that is to be sensed.

SUMMARY OF THE INVENTION

The invention provides various exemplary embodiments, including systems,methods, and apparatus. In general, the embodiments involve spreading oflight, such as light that is to be photosensed.

These and other features and advantages of exemplary embodiments of theinvention are described below with reference to the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a stimulus-wavelength converter devicewith output light being spread as it propagates to a light sensingassembly.

FIG. 2 is a schematic top view of a photosensor array that could be usedin the light sensing assembly of FIG. 1.

FIG. 3 is a schematic plan view of an integrated circuit (IC) with aphotosensor array that can be used in the light sensing assembly of FIG.1.

FIG. 4 is a schematic cross-sectional view of an implementation of anassembly that can be used in FIG. 1.

FIG. 5 is a graph illustrating laterally varying light transmissionproperties of a transmission structure as in FIG. 4.

FIG. 6 is a schematic cross-sectional view of another implementation ofan assembly that can be used in FIG. 1.

FIG. 7 is a graph illustrating the laterally varying light transmissionproperties of a transmission structure in FIG. 6.

FIG. 8 illustrates a technique that produces a transmission structurethat can be used in an assembly as in FIG. 1, showing orthogonalschematic cross-sectional views of deposition.

FIG. 9 illustrates another technique for producing a transmissionstructure that can be used in an assembly as in FIG. 1, showing twoschematic cross-sectional views of stages of the technique.

FIG. 10 is a schematic cross-sectional view of another implementation ofan assembly that can be used in FIG. 1.

FIG. 11 is a schematic top view of a mask that could be used to producea transmission structure as in FIG. 10.

FIG. 12 is a schematic side view of an implementation of a device as inFIG. 1.

FIG. 13 is a cross-sectional view of the implementation of FIG. 12,taken along the line 13-13.

FIG. 14 is a schematic side view of another implementation of a deviceas in FIG. 1.

FIG. 15 is a schematic side view of another implementation of a deviceas in FIG. 1.

FIG. 16 is a schematic side view of another implementation of a deviceas in FIG. 1.

FIG. 17 is a schematic side view of another implementation of a deviceas in FIG. 1.

FIG. 18 is a schematic top view of the implementation in FIG. 17.

FIG. 19 is a cross-sectional view of the implementation as in FIGS. 17and 18, taken along the lines 19-19.

FIG. 20 is a schematic top view of another implementation of a device asin FIG. 1.

FIG. 21 is a schematic side view of the implementation of FIG. 20.

FIG. 22 is a cross-sectional view of the implementation of FIGS. 20 and21, taken along the lines 22-22.

FIG. 23 is a schematic top view of another implementation of the deviceof FIG. 1.

FIG. 24 is a schematic side view of the implementation of FIG. 23.

FIG. 25 is a schematic top view of another implementation of the deviceof FIG. 1.

FIG. 26 is a schematic side view of the implementation of FIG. 25.

FIG. 27 is a cross-sectional view of the implementation of FIGS. 25 and26, taken along the lines 27-27.

FIG. 28 is a flow chart showing operations performed in producing andusing a device as in FIG. 1.

FIG. 29 is a schematic block diagram of a system that could control anumber of devices as in FIG. 1.

FIG. 30 is a schematic diagram of a camera that includes one or moredevices as in FIG. 1.

FIG. 31 is a graph showing results obtained from an implementation ofthe camera in FIG. 30.

FIG. 32 is a schematic side view of a test implementation of a device asin FIG. 1 with an assembly that includes a position sensor.

FIG. 33 is a graph showing response to change in wavelength for the testimplementation of FIG. 32.

FIG. 34 is a graph showing differential signal as a function of inputwavelength for another version of the test implementation of FIG. 32.

FIG. 35 is a graph showing differential signal as a function ofwavelength for a test implementation with an assembly that includescells as in FIG. 3.

FIG. 36 is a schematic diagram of a test implementation in which adevice like that in FIG. 1 was implemented to measure temperature.

FIG. 37 is a graph showing signal response over time for the testimplementation of FIG. 36.

FIG. 38 is a graph showing differential signal as a function oftemperature for the test implementation of FIG. 37.

FIG. 39 is a schematic side view of an implementation of a device likethat in FIG. 1 to obtain information from a well plate.

DETAILED DESCRIPTION

In the following detailed description, numeric values and ranges areprovided for various aspects of the implementations described. Thesevalues and ranges are to be treated as examples only, and are notintended to limit the scope of the claims. In addition, a number ofmaterials are identified as suitable for various facets of theimplementations. These materials are to be treated as exemplary, and arenot intended to limit the scope of the claims.

“Light” refers herein to electromagnetic radiation of any wavelength orfrequency; unless otherwise indicated, a specific value for lightwavelength or frequency is that of light propagating through vacuum. Theterm “photon” refers herein to a quantum of light, and the term “photonenergy” refers herein to the energy of a photon. Light can be describedas having a “photon energy distribution”, meaning the combination ofphoton energies that are included in the light; highly monochromaticlight, for example, has a photon energy distribution with one peakenergy value.

To “propagate” light through a region or structure is to transmit orotherwise cause the light to propagate through the region or structure.The light may be referred to as “propagated light” or “propagatinglight”.

“Photon energy information” refers herein to information about photonenergy, such as information about wavelength, frequency, wavelengthshift, frequency shift, or a distribution of wavelengths or frequencies.“Absolute photon energy information” is information about a given photonenergy value, such as a specific wavelength or frequency, while“relative photon energy information” is information that relates twophoton energy values, whether measured concurrently or at differenttimes.

The interchangeable terms “wavelength shift”, “frequency shift”, and“photon energy shift” all refer to a shift between photon energies,which is one example of a “change” in photon energy distribution. Moregenerally, a “change” in photon energy distribution occurs whenever aphoton energy distribution before an event and a photon energydistribution after the event cannot be made congruent by performingsubstantially the same normalization at all points in one of thedistributions.

The various exemplary implementations described below address problemsthat arise in reading out photon energy information such as wavelengthor wavelength shift information, such as from stimulus-wavelengthconverters of the types described in the above-cited article by Fuhr andbook by Othonos and Kalli. One of those problems is the difficulty ofobtaining high relative wavelength resolution rapidly and without bulky,expensive equipment; for example, it is difficult to read outinformation about very small (e.g. approximately 10⁻⁴ nm to a few nm)wavelength shifts. Another is the difficulty of obtaining high absolutewavelength resolution. It can also be problematic to provide sensitivityto wavelength and not to intensity of incident light.

The term “sensing” is used herein in the most generic sense of obtaininginformation from a physical stimulus; sensing therefore includes actionssuch as detecting, measuring, and so forth. To “photosense” is to sensephotons, and to “photosense quantity” of photons is to obtaininformation indicating a quantity of the photons. Photons that arephotosensed are sometimes referred to herein as “incident photons”.

A “photosensor” is used herein to refer generally to any element orcombination of elements that senses photons, whether by photosensingquantity or any other information about the photons. A photosensorcould, for example, provide an electrical signal or other signal thatindicates sensed information, such as a signal indicating quantity ofincident photons. A photosensor that provides electrical signalsindicating position, such as of a high-intensity light spot, is referredto herein as a “position sensor”. If electrical sensing events occur ina photosensor in response to incident photons, the photosensor mayintegrate or otherwise accumulate the results of the electrical sensingevents during a time period referred to herein as a “sensing period”.

In contrast to photosensing, “stimulus-wavelength conversion” refers toa form of sensing that, in response to a stimulus, provides informationabout the stimulus through photon energies of output light, such asthrough wavelength or wavelength shift in output light; such informationis referred to herein as “wavelength information”. The wavelengthinformation can indicate any of various characteristics of the stimulus,such as timing, magnitude, or polarity of a stimulus change, magnitudeor polarity of an stable stimulus, and so forth. A “stimulus-wavelengthconverter” is a sensor that performs stimulus-wavelength conversion.

A “range of photon energies” or an “energy range” is a range of energyvalues that photons can have. An energy range can be described, forexample, as a range of wavelengths or a range of frequencies or, inappropriate cases, by the range's central wavelength or frequency andpossibly also the range's width. A “subrange” of a range of photonenergies is a part of the range, and can be similarly described.

In general, the upper and lower boundaries and widths of ranges andsubranges are approximate. To provide output photons or to photosensequantity of photons “throughout”, “within”, or “in” a range or subrangemeans to provide photons or to obtain information about quantity ofphotons that are predominantly within the range or subrange. In typicalcases, between 60-90% of the provided photons or sensed quantity ofphotons have energies within the range or subrange, but the percentagecould be lower or higher. In some applications, 90% or even 95% or moreof the provided photons or sensed quantity of photons have energieswithin the range or subrange. Where an application requires that aminimum percentage or other proportion of provided photons or sensedquantity of photons have energies within a range or subrange, theminimum percentage or other proportion is referred to herein as the“application's minimum photon proportion”.

Some of the photosensing implementations described herein employstructures with one or more dimensions smaller than 1 mm, and varioustechniques have been proposed for producing such structures. Inparticular, some techniques for producing such structures are referredto as “microfabrication.” Examples of microfabrication include varioustechniques for depositing materials such as growth of epitaxialmaterial, sputter deposition, evaporation techniques, platingtechniques, spin coating, printing, and other such techniques;techniques for patterning materials, such as etching or otherwiseremoving exposed regions of thin films through a photolithographicallypatterned resist layer or other patterned layer; techniques forpolishing, planarizing, or otherwise modifying exposed surfaces ofmaterials; and so forth.

In general, the structures, elements, and components described hereinare supported on a “support structure” or “support surface”, which termsare used herein to mean a structure or a structure's surface that cansupport other structures. More specifically, a support structure couldbe a “substrate”, used herein to mean a support structure on a surfaceof which other structures can be formed or attached by microfabricationor similar processes.

The surface of a substrate or other support surface is treated herein asproviding a directional orientation as follows: A direction away fromthe surface is “up”, “over”, or “above”, while a direction toward thesurface is “down”, “under”, or “below”. The terms “upper” and “top” aretypically applied to structures, components, or surfaces disposed awayfrom the surface, while “lower” or “underlying” are applied tostructures, components, or surfaces disposed toward the surface. Ingeneral, it should be understood that the above directional orientationis arbitrary and only for ease of description, and that a supportstructure or substrate may have any appropriate orientation.

An “integrated circuit” or “IC” is a structure with electricalcomponents and connections produced by microfabrication or similarprocesses. An IC may, for example, be on or over a substrate on which itwas produced or another suitable support structure. Other componentscould be on the same support structure with an IC, such as discretecomponents produced by other types of processes.

Implementations described herein include features characterized as“cells” and “arrays”, terms that are used with related meanings: An“array” is an arrangement of “cells”. An array on an IC or other supportsurface may also include circuitry that connects to electricalcomponents within the cells such as to select cells or transfer signalsto or from cells, and such circuitry is sometimes referred to herein as“array circuitry”. In contrast, the term “peripheral circuitry” is usedherein to refer to circuitry on the same support surface as an array andconnected to its array circuitry but outside the array. The term“external circuitry” is more general, including not only peripheralcircuitry but also any other circuitry that is outside a given cell orarray.

Some of the implementations below are described in terms of “rows” and“columns”, but these terms are interchangeable. Also, rows and columnsare described herein as examples of “lines”. Within an array, a “line”of cells refers herein to a series of cells through which a line can bedrawn without crossing areas of cells that are not in the line. Forexample, in a two-dimensional array in which cells have uniform areas, aline of cells could be a row, a column, a diagonal, or another type ofstraight line; more generally, a line of cells could be straight orcould include one or more non-straight features, such as curves orangles.

A “photosensor array” is an array in which some or all of the cells areor include photosensors. Accordingly, an IC “includes” a photosensorarray if the IC includes an array of cells, and at least some of thecells include respective photosensors. A cell that includes aphotosensor may also include “cell circuitry”, such as circuitry thatmakes connections with the photosensor, that transfers signals to orfrom the photosensor, or that performs any other function other thanphotosensing. In general, a cell's photosensor and cell circuitry arewithin a bounded area of the array, an area sometimes referred to hereinas the “cell's area”. The part of a cell's area in which an incidentphoton can be photosensed is referred to herein as “sensing area”.

In an application of an IC that includes a photosensor array, circuitrythat “responds to” one or more photosensors can be any circuitry that,in operation, receives information from the photosensors about theirphotosensing results through an electrical connection. Circuitry thatresponds to a photosensor could be circuitry in the same cell as thephotosensor, or it could be array circuitry, peripheral circuitry, orother external circuitry, or it could include any suitable combinationof cell circuitry, array circuitry, peripheral circuitry, and otherexternal circuitry.

FIGS. 1 and 2 illustrate general features of a stimulus-wavelengthconversion device 10. Device 10 includes stimulus-wavelength converter12 and readout components 14.

As schematically shown by arrow 20 in FIG. 1, converter 12 receives astimulus, such as the presence, absence, quantity, or concentration ofan analyte. Within converter 12, an interaction occurs in response tothe stimulus, as represented schematically by circle 22, with the resultthat output light, represented by ray 24, includes wavelengthinformation or other photon energy information about the stimulus.Specifically, the output light could undergo a wavelength shift inresponse to a change in the stimulus. The stimulus could be any of amultitude of types, including but not limited to temperature, pressure,stress, strain, flow, level, speed or rpm, position, orientation,motion, acceleration, presence or absence of an analyte, rain,thickness, liquid quality, breakage, or magnetic field.

Within converter 12, the stimulus could affect photon energies in theoutput light in any of numerous ways, some of which are described in theabove-cited article by Fuhr and book by Othonos and Kalli. For example,converter 12 could include a surface or point at which broadband inputlight is partially reflected to provide output light, as can occur in anFBG or photonic crystal sensor. Or light could be generated withinconverter 12 to provide output light, as can occur in a laser cavity. Orfluorescence within converter 12 could provide output light. Orbroadband input light could be transmitted through a Fabry-Perot-typestructure to provide output light. In each case, the stimulus affectsphoton energies in the output light from converter 12; for example, thestimulus could affect the laser cavity, could be presence or absence ofa fluorescent analyte, or could change the cavity of the Fabry-Perotstructure.

Readout components 14 could be implemented in many ways, and FIG. 1illustrates some components that may occur in exemplary implementations.Propagation component 30 receives output light from converter 12 andpropagates the output light to other components, as suggested by rays32.

As used herein a “light propagation component” or simply “propagationcomponent” is any feature, surface, interface, layer, lens, transmissionstructure as described below, or other component that provides light inresponse to received light. In general, a light propagation componenthas an “entry surface”, meaning a surface at which it receives enteringlight, and an “exit surface”, meaning a surface at which it providesexiting light. Between its entry and exit surfaces, a propagationcomponent can perform one or more functions on the light, includingtransmitting, guiding, collimating, imaging, focusing, spreading, and soforth. For example, a propagation component could include one or moreoptical fibers to transmit output light from converter 12 between itsentry surface and an assembly of other components at its exit surface.

In the example illustrated in FIG. 1, rays 32 diverge within component30, suggesting that component 30 spreads output light from converter 12,but component 30 could direct the output light in any other appropriateway, as illustrated in greater detail by examples set forth below. Asused herein a “light spreading component” or simply “spreadingcomponent” is a propagation component for which the exiting light'sintensity distribution at any given time has a greater variance in atleast one direction than the entering light to which it responds, wherevariance is expressed as a distance across the respective surface. Theexiting light from a spreading component can be described as “spreaded”over a greater extent of the exit surface than the entering lightoccupies in the entry surface, though the entry and exit surfaces may beclosely spaced surfaces in some implementations. Spreading can also bedescribed as occurring “in a” direction, meaning that increase invariance occurs in the direction; a direction in which spreading occursmay be straight, but rather could be curved or angled.

Light sensing assembly 34 receives the output light, such as afterspreading by component 30, and, in response, provides electrical signalsthat indicate information about the stimulus. Assembly 34 illustrativelyincludes laterally varying transmission structure 40. A structure that“transmits” photons, sometimes referred to herein as a “transmissionstructure”, is any material structure through which light can propagate.It is not necessary that there be a one-to-one relationship betweenphotons that enter a transmission structure and photons that exit fromit as long as the structure provides exiting photons in response toentering photons as a result of light propagation through the structure.

More generally, to “transmit” photons is to perform a function by whichexiting photons at an exit position are provided in response to enteringphotons at an entry position as a result of light propagation betweenthe entry and exit positions. To “transmit only” a specified set ofphotons from a first position to a second refers to a function thattransmits photons from the first position to the second, butpredominantly photons in the specified set. As with providing photonsand photosensing, described above, if a transmission structure transmitsonly a specified set of photons, between 60-90% of the transmittedphotons are in the specified set, but the percentage could be lower orhigher. In some applications, 90% or even 95% or more of the photons arein the specified set.

One type of transmission structure is a “coating”, meaning a layeredstructure of light-transmissive material that is on or over anothercomponent such as a photosensor array or position sensor. Variousexamples of coatings are described below.

A transmission structure provides (and a photosensor receives from atransmission structure) photons “throughout”, “within”, or “in” a rangeor subrange if the provided photons are predominantly within the rangeor subrange. As in other contexts described above, between 60-90% of thephotons from a transmission structure typically have energies within therange or subrange, but the percentage could be lower or higher. In someapplications, 90% or even 95% or more of the photons have energieswithin the range or subrange.

A transmission structure can be characterized by an “energy transmissionfunction” or simply “transmission function” that relates positions inthe transmission structure to photon energies that are transmitted atthe positions. For example, if a position transmits photons within aspecific subrange but not outside the specific subrange, thetransmission function at that position passes the specific subrange butnot other subranges.

A transmission structure is “laterally varying” if its transmissionfunction varies as a function of position within its exit surface, suchposition being referred to herein as “lateral position”. The variationin transmission function can, for example, vary according to a gradient,which can be a “constant transmission gradient” if it variescontinuously or uniformly in a lateral direction or a “step-liketransmission gradient” if it varies in a step-like manner in a lateraldirection. Where a transmission structure is two-dimensional, it couldhave a constant transmission gradient in one lateral direction and astep-like transmission gradient in another. In general, a transmissionfunction “varies in a” direction if it varies along a line that extendsin the direction; a direction in which a transmission function may bestraight, but rather could be curved or angled.

In addition to having a laterally varying energy transmission function,a transmission structure may also transmit light as a function ofincident angle. This can also be a source of lateral inhomogeneity intransmission, for example, of light from a point-like source, becausethe light will have different incident angles at different positions onthe transmission structure's entry surface. A transmission structure maytherefore be described as “laterally inhomogeneous” if it has alaterally varying energy transmission function, if it transmits light asa function of incident angle, or both.

Structure 40 transmits photon energies as a function of lateral positionand therefore is laterally inhomogeneous. This feature is illustrated inFIG. 1 by regions 42 and 44 in structure 40. As shown, region 42transmits light in a subrange centered about wavelength λ_(a).Similarly, region 44 transmits light in a subrange centered aboutwavelength λ_(b). As a result, the light from regions 42 and 44,represented respectively by rays 46 and 48, is incident on photosensingcomponents 50 at different positions, represented respectively byposition 52 and position 54. Therefore, if a change in the stimuluscauses a change in photon energy between λ_(a) and λ_(b), this changewill be indicated by a change in the light detected at positions 52 and54.

FIG. 1 therefore illustrates the importance of spreading light to besensed by assembly 34: If the output light from converter 12 were notspreaded over the entry surface of transmission structure 40, but wereinstead incident only on a small area of transmission structure 40, thelight would only reach a corresponding small area of photosensingcomponents 50. In this case, the wavelength information that wouldotherwise be sensed in other areas of photosensing components 50 wouldbe lost. In other words, spreading is necessary so that photosensingcomponents 50 can provide signals that accurately indicate wavelengthinformation from the output light.

Photosensing components 50 could be implemented in many ways, includingwith various ICs that include photosensor arrays or position sensors.FIG. 2 shows array 60, an example of a photosensor array that couldimplement photosensing components 50.

Array 60 in FIG. 2 includes cells 62 and 64, labeled to show that cell62 is at position 52 in FIG. 1, and therefore receives predominantlylight in a subrange around wavelength λ_(a), while cell 64 is atposition 54 and receives predominantly light in a subrange aroundwavelength λ_(b). Output light from converter 12 could, for example,have or be provided about one or more “peak energy values” in a givenapplication, meaning central values of photon energy subranges in whichintensity can significantly exceed intensities in nearby subranges. Ifthe output light has two peak energy values λ_(a) and λ_(b) for tworespective values of stimulus 22 (e.g. presence and absence, twoquantities, or two concentrations of an analyte), then a change betweenthe stimulus values would result in a wavelength shift between λ_(a) andλ_(b), resulting in a change in quantities of photons sensed by cells 62and 64. Similarly, output light from converter 12 could be in a “narrowband” of energies in a given application if it has a peak energy valueand the subrange in which intensity significantly exceeds nearbyintensities is approximately one-tenth or less of the application'senergy range; in contrast, “broadband” generally refers to light thathas an energy distribution that is more uniform than narrow band lightacross a relatively broad energy range and that contains a significantlight intensity in all energy subranges of interest.

More generally, a wavelength shift between wavelengths λ_(a) and λ_(b)or another change in photon energy distribution at the input surface oftransmission structure 40 can change “relative quantities” of photonsprovided at positions 52 and 54, meaning that the quantities provided atthe two positions have a different relation to each other after theshift than they did before it. For example, the quantities couldincrease or decrease, but by amounts such that the quantity at oneposition becomes a larger or smaller fraction of the quantity at theother position; the quantity at one location could change from beingless than the quantity at the other position to being greater; or onequantity could increase while the other decreases; etc.

FIG. 2 also shows how the quantities of photons sensed by cells 62 and64 can be compared, such as by comparator 70. Comparator 70 could, forexample, be biased so that the output signal on line 72 indicates astimulus change of a particular type that causes a wavelength shiftbetween wavelengths λ_(a) and λ_(b).

As used herein, an operation or a component of circuitry “compares” ifthe result indicates a relationship between signals or values beingcompared, such as difference, equality, which is greater, which is less,whether the difference is greater or less than a quantity or meets someother criterion, and so forth.

If it indicates the difference between the photosensed quantities ofcells 62 and 64, the value of the output signal on line 72 would be anexample of a “differential quantity”, which refers herein to a valuethat indicates a difference between two quantities. A differentialquantity could, for example, be an unbiased or biased analog outputvalue from a differential amplifier or other analog comparator; a simpledifference obtained by subtraction of two digital values, one or both ofwhich could be normalized or otherwise adjusted; a ratio obtained byanalog or digital circuitry; a value obtained by combining relateddifferential quantities, such as differences between each quantity and athird quantity; or any other analog or digital value that includesinformation about the difference. A “differential signal” generallyrefers herein to a signal that indicates a differential quantity.

Although represented in FIG. 1 simply as a box, converter 12 could beimplemented in numerous ways, including FBGs, POFs, photonic crystals,and various optical biosensors, as mentioned above. As described ingreater detail below, however, the design of readout components 14depends primarily on the properties of output light from converter 12,such as whether it is monochromatic or broad spectrum and whether it isparallel or divergent. Other factors affecting the design of readoutcomponents 14 include wavelength resolution and energy range.

If converter 12 is a single fiber with a single FBG, the output lightwill be point-like and monochromatic. For this type of sensor,propagation component 30 can spread the output light over substantiallythe whole area of laterally varying transmission structure 40, so thatthe position of the transmitted light spot on photosensing components 50corresponds with the wavelength of the output light. Photosensingcomponents 50 could be implemented as a one-dimensional photosensorarray with a coating as described below. In addition, photosensingcomponents 50 could alternatively be implemented as a position sensor,as described in co-pending U.S. patent application Ser. No. 10/922,870,entitled “Chip-size Wavelength Detector” and incorporated herein byreference in its entirety.

If converter 12 is a single fiber with multiple FBGs, it can provide apoint-like output light with multiple photon energies. As in theprevious example, propagation component 30 can spread the output lightover substantially the entire area of laterally varying transmissionstructure 40, and photosensing components 50 can be implemented with anarray like photosensor array 60, with each cell sensitive to arespective energy subrange. More specifically, photosensing components50 can be implemented with a one-dimensional photosensor array with acoating as described below.

If converter 12 is a fiber bundle with a single FBG in each individualfiber, the output light will include several monochromatic point-likeoutputs. Propagation component 30 can spread the light from eachpoint-like output over a respective region of laterally varyingtransmission structure 40. Cross-talk between the different lightoutputs can be minimized by special optics or blades as described below.For each region of transmission structure 40, photosensing components 50can include a respective set of sensing locations. Photosensingcomponents 50 could be implemented, for example, as a two-dimensionalphotosensor array with a coating as described below. Alternatively, acoated position sensor array could be used, containing a number ofposition sensor elements as described in co-pending U.S. patentapplication Ser. No. 10/922,870, entitled “Chip-size WavelengthDetector” and incorporated herein by reference in its entirety. Thesetechniques may also be appropriate for a converter that provides asingle point-like output with a very large photon energy range.

If converter 12 is a fiber bundle with multiple FBGs per fiber, theoutput light will include several point-like outputs, each with multiplephoton energies. Propagation component 30 can spread the light from eachoutput over structure 40 such that one respective row of a photosensorarray within components 50 receives the light from each output.Photosensing components 50 could be implemented as a two-dimensionalphotosensor array or CCD IC with a coating as described below.Cross-talk between the different light outputs can be minimized byspecial optics or blades as described below. These techniques may alsobe appropriate for a converter that provides a single point-like outputwith a very large photon energy range.

Converters can provide output light in various ways other than by fiberend facets and point-like sources. As described below, for example, aconverter may provide output light through a broad area source otherthan a fiber end facet, where the term “broad area source” means asource that has sufficient two-dimensional extent that it cannot beapproximated by a single point-like source. Techniques as describedbelow could be applied, for example, to a broad area source thatprovides substantially the same photon energy distribution throughoutits area. In some techniques, a broad area source could be attacheddirectly to light sensing assembly 34.

The principles set forth above can also be applied to converters otherthan FBGs, such as POFs, photonic crystals, and optical biosensors. Ineach case, an appropriate combination of components can be used toobtain satisfactory sensing and readout.

Photosensing components 50 can include various photosensitive elements,chosen to be appropriate for the incident light intensity. For low powerincident light, exemplary solutions include: (1) a small detectorsurface area, which is beneficial because the total light is notdistributed over a large area and the intensity per unit area stayshigh—this solution is also inexpensive, but, due to a limited detectorsize, the wavelength range and resolution may also be limited; (2)arrays such as cooled CCDs, avalanche photodiodes, and photomultipliertubes (PMTs) that provide increased signal-to-noise ratio but areexpensive; or (3) intensified CCD arrays that enable single photoncounting but are very expensive.

Light sensing assembly 34 in FIG. 1 can therefore be implemented in awide variety of ways, including various types of photosensor arrays andposition sensors. FIG. 3 is a schematic view of an exemplary IC with aphotosensor array that can be used in some such implementations. FIGS.4-11 illustrate various implementations of assembly 34 that can includean IC like that shown in FIG. 3, or that could alternatively beimplemented with position sensors as described in co-pending U.S. patentapplication Ser. No. 10/922,870, entitled “Chip-size WavelengthDetector” and incorporated herein by reference in its entirety.

IC 90 in FIG. 3 includes photosensor array 100, which is illustrativelya two-dimensional array, with at least two rows of cells that includephotosensors. Different rows or other parts of array 100 can be providedwith different coatings or can be otherwise structured so that theircells photosense different ranges or subranges of photon energies. As aresult, the information obtained from a single IC can provide a detailedanalysis of incident photons over a broad range of photon energies. Inaddition, reference cells, such as the cells in row 102, can be used toprovide a spatially resolved real-time reference signal.

Within an array, a “pair” of cells is any two cells; unless otherwisespecified, the cells in a pair need not have any other specificrelationship to each other. The cells in a pair are “near each other” ifthe distance between them meets a suitable criterion for nearness, suchas being no greater than ten times the maximum diameter of the larger ofthe cells. In general, for example, two cells that are adjacent are alsonear each other. More generally, a set of cells are all “nearby” anothercell if each cell in the set and the other cell, taken as a pair, arenear each other. A feature of array 42 is that it includes one or morereference cells that are nearby to a subrange cell, such as by beingadjacent to the subrange cell.

Each cell in row 102 photosenses photons throughout a suitable range,characterized as λ_(all), to produce a reference for a nearby cell inrow 104. For implementations in which it is advantageous to have signalstrengths of the same order from a cell in row 102 and its paired cellin row 104, the cell in row 102 must be different from the cells in row104. For example, it could have a different sensing area or it couldhave a gray filter coating different than a coating over the paired cellin row 104.

Each cell in row 104, on the other hand, photosenses a respectivesubrange between λ_(min) and λ_(max), with illustrative cell 106photosensing a subrange centered around λ_(p). IC 90 also includes arraycircuitry (not shown) as well as peripheral circuitry 110 which performvarious functions relating to readout of photosensed information fromarray 100.

One advantage of the technique illustrated in FIG. 3 is that IC 90provides a compact photosensor array that can be used within a device,such as in a stimulus change sensing device. Results from more than onesuch IC within a device may be combined to obtain more complete sensing.In general, photosensed quantities or other results of photosensing are“combined” when they are included together in any data structure orsignal, possibly after one or more data processing or signal processingoperations.

FIG. 4 illustrates an implementation of assembly 34, showing in greaterdetail how cells of an array photosense subranges, such as in row 104 inFIG. 3. As in other implementations described herein, assembly 34 inFIG. 4 can be supported by a suitable support component.

In FIG. 4, a cross-section has been taken through a fragment 150 of aphotosensor array, with cells 152 of the fragment 150 shownschematically in cross-section. Over cells 152 is a transmissionstructure 160 that receives incident light 162, such as from any of thebelow-described implementations for receiving light from astimulus-wavelength converter.

Transmission structure 160 can, for example, be a film with laterallyvarying light transmission properties as described, for example, inco-pending U.S. patent application Ser. No. 10/922,870, entitled“Chip-size Wavelength Detector” and incorporated herein by reference inits entirety. In the portion of transmission structure 160 shown in FIG.4, wedge-shaped transmissive cavity 170 is enclosed between reflectivefilms 172 and 174, forming a wedge-shaped Fabry-Perot etalon. Becauseits thickness varies as a function of position along the y-axis,transmission structure 160 will transmit different wavelengths as afunction of position along the y-axis. Such a function is sometimesreferred to herein as a “wavelength-position function”.

Transmission structure 160 can be produced with appropriate coatings onor over a photosensor array. Films 172 and 174 and cavity 170 could allbe produced, for example, by exposure to deposition beams in anevaporation chamber; films 172 and 174 with uniform thicknesses could beproduced by appropriate on-axis deposition, while cavity 170 withlaterally varying thickness can be produced by appropriate off-axisdeposition. FIG. 4 illustratively shows films 172 and 174 as relativelythick compared to cavity 170, which would be appropriate for layers ofnon-metallic material such as SiO₂, TiO₂, or Ta₂O₅, with thicknessesdesigned as described below; such materials are typically used toproduce Bragg mirrors by depositing thin alternating layers with lowabsorption coefficients and large differences in refractive indices. Iffilms 172 and 174 are reflective metal, however, they could be muchthinner.

For an implementation with non-metallic material, specific thicknessesof cavity 170 and films 172 and 174 could be designed from the desiredtransmitted wavelength λ and the refractive index n of cavity 170. Thethickness of cavity 170 is typically chosen to be λ/(2n) or an integermultiple thereof, while the thicknesses of Bragg mirror layers withinfilms 172 and 174 are typically λ/(4n). The number of pairs of suchlayers in each of films 172 and 174 can vary between a few (e.g. 2-5)all the way up to 20 or 30, depending on the difference in refractiveindex between the two materials used, the desired transmission bandwidth, and the desired stop band reflectivity. Therefore, in typicalimplementations, films 172 and 174 are much thicker than cavity 170, assuggested in FIG. 4.

FIG. 5 illustrates the laterally varying light transmission propertiesof transmission structure 160. Because its thickness varies as afunction of position along the y-axis, cavity 170 transmits differentwavelengths as a function of position along the y-axis. Wavelengths ofphotons predominantly transmitted to nine of cells 152 as in fragment150 are illustrated by the low reflectivity minima labeled 1 through 9.As can be seen, the high-transmissivity photon energy range fortransmission structure 160 varies laterally.

FIG. 6 illustrates another implementation of assembly 34, with featuresthat have the same reference numbers as in FIG. 4 being implemented asdescribed above. Rather than transmission structure 160, however,assembly 34 includes transmission structure 180. Transmission structure180 can, for example, be a laterally graded Bragg mirror in which eachof layers 182, 184, 186, and 188 is laterally graded. Each of layers182, 184, 186, and 188 could be produced as described above for cavity170, using off-axis deposition in an evaporation chamber.

FIG. 7 illustrates the laterally varying light transmission propertiesof transmission structure 180. Because its thickness varies as afunction of position along the y-axis, transmission structure 180reflects different wavelengths as a function of position along they-axis. Curves 200, 202, 204, and 206 are shown, representingreflectivity of the portion of transmission structure 180 over each offour cells 152 in fragment 150, with curve 200 being for the leftmostcell of the four in FIG. 6 and curve 206 being for the rightmost cell ofthe four. As can be seen, the high-reflectivity photon energy range fortransmission structure 180 varies laterally.

FIG. 8 illustrates a technique that produces transmission structure 210with laterally varying light transmission properties similar to thoseillustrated in FIGS. 5 and 7 but with lateral variation in each of twodimensions. This technique can be used to produce different coatings fordifferent rows of a photosensor array so that their cells photosensedifferent ranges or subranges of photon energies, and can be usedseparately or in combination with reference cells.

Transmission structure 210 is produced on or over cells 152 ofphotosensor array 150 by using deposition source 212 to providedeposition beam 214 that can be characterized at any given point on thesurface of structure 210 by two angles. One of the two angles resultsfrom angular variation of deposition beam 214 in the x-direction acrossarray 150, while the other results from angular variation in they-direction. As a result, the thickness gradient of structure 210 issimilarly different in the x- and y-directions. Therefore, cells withineach row extending in the y-direction will photosense a range of photonenergies similarly to FIG. 7, but the range will be different than therange photosensed by cells in any other row extending in the samedirection.

The technique of FIG. 8 could be implemented in a variety of ways. Forexample, during deposition, structure 210 could be formed on a supportstructure that is tilted as required, deposition source 212 could betilted as required, or both kinds of tilt could be employed.

FIG. 9 illustrates a technique that produces transmission structure 220with laterally varying light transmission properties similar to thoseillustrated in FIGS. 5 and 7 but without variation in thickness oftransmission structure 220. The technique in FIG. 9 can be characterizedas providing laterally varying optical thickness d*n, where d isthickness and n is index of refraction, but without actual variation inthickness d. In contrast, the techniques of FIGS. 4-8 provide varyingoptical thickness by providing actual variation in thickness.

In the upper part of FIG. 9, homogeneous coating 222 is deposited bydeposition source 224, which provides deposition beam 226 uniformly overthe surface of photosensor array 150 similar to those in FIGS. 4, 6, and8. This operation could, for example, be implemented with conventionaldeposition techniques.

Then, in the lower part of FIG. 9, light source 230 is scanned acrossthe coating over array 150 to introduce a laterally varying change ofrefractive index in resulting transmission structure 220. For example,source 230 can be an ultraviolet source that provides intensity I with aconstant value along each line parallel to the x-axis (perpendicular tothe plane of FIG. 9), but varying from I_(min) for lines nearer thex-axis to I_(max) for lines farther from the x-axis, as shown in FIG. 9by the values along the y-axis. As a result, the wavelengths transmittedto cells in array 150 can vary along the y-axis from λ_(min) to λ_(max),as shown. The same pattern of intensity can be concurrently applied bysource 230 to each of a number of arrays that are appropriatelyarranged, allowing batch fabrication of arrays. Two-dimensionalvariation in optical density equivalent to that in FIG. 8 could also beobtained with two-dimensional variation in the ultraviolet source'sintensity.

FIG. 10 illustrates an implementation of assembly 34 that is similar tothe implementation of FIG. 4, but with a step-like gradient in they-direction which could be combined with a constant thickness in thex-direction or with a constant gradient in the x-direction as in theleft-hand side of FIG. 8. The arrangement in FIG. 10 can be used with aphotosensor array that has discrete photosensing cells, as illustratedby fragment 150 with cells 152. If used with a CCD or CMOS photosensorarray, cells under different steps will receive photons in differentenergy subranges of the range of photon energies incident upon assembly34.

In FIG. 10, in addition to the cross section through fragment 150, across section has been taken through transmission structure 240 thatreceives incident light 242, such as from any of the below-describedimplementations for receiving light from a stimulus-wavelengthconverter. Similarly to transmission structure 160 in FIG. 4,transmission structure 240 includes staircase-shaped transmission cavity244 enclosed between reflective films 246 and 248, forming astaircase-shaped Fabry-Perot etalon. Because its thickness varies as afunction of position along the y-axis, transmission structure 240 willtransmit different wavelengths as a function of position along they-axis.

FIG. 11 illustrates half-tone mask 250 that can be used in producingtransmission structure 240. For example, the technique in FIG. 9 couldbe modified by interposing mask 250 between deposition source 224 andarray 150 while depositing cavity 244 so that, rather than beinghomogeneous in thickness, coating 222 would have a step-like shape likestructure 240 in FIG. 10. As shown, mask 250 includes a series of Nrectangular regions 252 through 254, each of which has holes largeenough that material from deposition beam 226 can easily pass through.The density of the holes increases, however, from ρ₁ to ρ_(N), so thatthe thickness of cavity 244 also increases, and cavity 244 is thinnestunder region 252, becomes thicker under each successive region, and isthickest under region 254.

This technique can also be applied to achieve a continuous or uniformcavity gradient as depicted in FIG. 4. In this case, the density ofholes would increase continuously from ρ₁ to ρ_(N), so that thethickness of cavity 170 also increases gradually, and cavity 170 isthinnest at the left side of structure 160 and thickest and the rightside of structure 160.

A transmission structure of uniform thickness but with optical thicknesssimilar to that of transmission structure 240 can alternatively beproduced, for example, with a technique similar to that shown in FIG. 9.Rather than a uniformly varying radiation function with a constantgradient, light source 230 can provide a step-like radiation function,either by scanning or by concurrent radiation. Or light source 230 couldprovide a constant radiation function through a light absorbingstructure with a step-like absorption function.

The techniques illustrated in FIGS. 4-11 could be implemented in variousother ways, with different cells of a photosensor array or differentpositions of a position sensor photosensing slightly different subrangesof a range of photon energies. For example, additional details aboutvarious production and calibration techniques and characteristics oftransmission structures that could be employed are described inco-pending U.S. patent application Ser. No. 10/922,870, entitled“Chip-size Wavelength Detector” and incorporated herein by reference inits entirety.

If quantities photosensed by the cells are read out in parallel andcompared, such as in the way suggested in FIG. 2, wavelength shiftinformation about incident photons can be obtained. As illustrated inFIG. 3, nearby cells, such as in a parallel row, can photosensequantities of photons throughout the range of photon energies to providereference information. If adjacent cells in the array have overlappingsubranges, computational techniques such as deconvolution can be used toimprove accuracy.

In general, the resolution of a technique as in any of FIGS. 4-11depends heavily on the number of cells in an array, the full width halfmaximum (FWHM) of the transmission peak, and the peak shift per cell.The smaller the FWHM and the peak shift, the better the resolution. Onthe other hand, the totally covered spectral width can be enhanced byincreasing the FWHM and the peak shift per cell. Therefore, thetechnique can be customized to the needs of a specific application. Forexample, the use of a Fabry-Perot cavity as in FIG. 4 enables very highspectral resolution, while a version with multiple cavities and manylayers as in commercially available products will be favorable forapplications with low light intensities in combination with smallspectral resolution such as with fluorescence. With such an approach,the spectral width of the transmission window and the reflectivity ofthe stop band can be optimized separately, which may be advantageousbecause the reflectivity of the stop band determines stray lightsuppression. It would also be possible to use a single laterally gradeddistributed Bragg reflector (DBR) mirror as in FIGS. 6 and 7 to obtain aphotosensor array with high light sensitivity but limited wavelengthresolution, appropriate for fluorescence or luminescence sensing.

A particular advantage of optical stimulus shift sensing as in FIGS. 1and 2, when implemented with techniques similar to those of FIGS. 3-11,is that laterally varying transmission and reflection properties of thecoating over the photosensor array define a correlation between positionand photon energy. Therefore the spatially dependent signal from thephotosensor array contains information about wavelength shifts due tostimulus change.

In experimental implementations, a coating as in FIG. 4 typicallytransmits approximately 60% of photons in its respective subrange. Thesubranges can be chosen with wavelengths that span between 0.01 and tensof nanometers (nm), depending on the design and gradient of the coatingand the cell size of the photosensor array. Very high light yield can beachieved by using a highly sensitive photosensor, such as an avalanchephotosensor array.

In contrast to transmission structures 160, 180, 210, 220, and 240, anycoating or other transmission structure over row 102 in FIG. 3 mustfunction as a gray filter across the range λ_(all) in order to provide asuitable reference. It may also be possible to leave row 102 uncoated insome implementations.

Techniques involving optical stimulus change measurement by photosensingin subranges to obtain wavelength shift information, as exemplified bythe implementations in FIGS. 1-11, can be implemented in many differentways for a wide variety of applications. For example, photons incidenton assembly 34 could be obtained in many different ways, some of whichare described below.

FIGS. 12-27 illustrate examples of how output light from astimulus-wavelength converter can be provided to an assembly such asassembly 34 as described above. Some of the examples include spreadingcomponents, as explained in greater detail below. In addition to thesteepness of a coating gradient and the length of a photosensor array,light beam geometry plays an important role in resolution of photonenergies, also referred to as “wavelength resolution.” For optimalperformance, the light beam would be perfectly parallel, as could beproduced with an appropriate lens system. For many applications,however, absolute wavelength resolution is not very critical, and theoptical components are not as important.

The various alternative implementations described below typically do notrequire optics if the output light from the converter is alreadyparallel, but divergent beams are more typical. Although the examplesbelow are described in terms of output light from optical fiber endings,point-like outputs, broad area sources, or arrays of one of these, thesame or similar configurations could be used for output light fromintegrated optical components such as waveguides, for photonic crystals,for optical biosensors, and so forth. Also, output light from anon-fiber stimulus-wavelength converter could be coupled into one ormore optical fibers and transmitted or guided by the fibers to a lightsensing assembly. For example, the reflected light from a photoniccrystal sensor can be either directly incident on a light sensingcomponent or can be transmitted to a light sensing component via anoptical fiber. In a specific example, a photonic crystal can include adielectric material with a high refractive index that is periodicallyaltered with another material or, for example, air; the spacing of theresulting periodic features within the dielectric material is betweenapproximately 10 nm and 1000 nm.

In FIG. 12, photosensor array 260 is covered by coating 262, a laterallyvarying transmission structure implemented in any of the ways describedabove. Fiber 270 provides the light output from a stimulus-wavelengthconverter of any of the types described above, and could alternativelybe any other type of broad area output light source, whether homogeneousor inhomogeneous; if inhomogeneous, quantities photosensed by referencecells can be used to adjust quantities photosensed by subrange cells, asmentioned above in relation to the reference cells in FIG. 3. In anycase, the end of fiber 270 is positioned as close as possible to thesurface of coating 262. As shown by the cross-sectional view in FIG. 13,fiber 270 can have approximately the same cross-sectional area as thearea of array 260, so that light from fiber 270 can be spreaded acrossapproximately the entire surface of coating 262. This configurationprovides cheap and simple alignment, but is not suitable for highwavelength resolution. Fiber 270 could be any appropriate fiber, such asa glass or polymer optical fiber. In this configuration, spreading ofoutput light occurs at the interface between fiber 270 and coating 262,because the surface of fiber 270 disposed toward coating 262 functionsas a spreading component.

In FIG. 14, output light source 280 is a point-like output such as anLED or an optical fiber that provides a divergent output light beam andis positioned a sufficient distance from coating 262 to illuminate theentire sensing area of photosensor array 260. As in the implementationof FIGS. 12 and 13, this implementation allows cheap and simplealignment, but is not suitable for high wavelength resolution. In thisconfiguration, spreading of output light occurs in the distance or gapbetween source 280 and coating 262, because air, gas, a transparentmedium, or vacuum in the gap functions as a spreading component.

In FIG. 15, lens 282 is positioned between output light source 280 andcoating 262, making the divergent beam from source 282 parallel. Thisconfiguration also allows for a simple alignment, and, in addition,makes it possible to obtain high wavelength resolution. In thisconfiguration, spreading of output light occurs in the distance or gapbetween source 280 and lens 282, because air, gas, a transparent medium,or vacuum in the gap functions as a spreading component. In analternative implementation, lens 282 actually images a broad area lightsource (e.g. a fiber end facet) onto coating 262.

In FIG. 16, optical component 284 is positioned between point-likeoutput light source 280 and coating 262, and can be a SELFOC® orgradient index (GRIN) lens that makes the divergent beam from source 280parallel. This configuration has the same advantages as that of FIG. 15,but the sizes of lenses that can be used in this configuration arelimited to those that are available. Additionally, this configurationenables more robust implementations in which all components are attachedto each other; this is possible, for example, using a commerciallyavailable GRIN lens with its focal point right at its surface. In thisconfiguration, spreading of output light occurs within lens 284 nearsource 280, because that region of lens 284 functions as a spreadingcomponent.

FIGS. 17-19 illustrate an implementation similar to FIG. 12, but with abundle 290 of glass or polymer optical fibers butt-coupled, i.e.positioned with their ends as close to coating 262 as possible. In theillustrated example, bundle 290 includes fibers 292, 294, and 296, andphotosensor array 260 can have an optical thickness gradient in they-direction and a homogeneous coating in the x-direction. This enablessensing of the same photon energy ranges for all fibers; an additionalgradient in the x-direction as in FIG. 8 would enable sensing ofdifferent photon energy ranges for different fibers. As in FIG. 12, thisconfiguration allows for cheap and simple alignment, but is not suitedfor high wavelength resolution. In this configuration, spreading ofoutput light occurs at the interfaces between fibers 292, 294, and 296and coating 262, because the surfaces of fibers 292, 294, and 296disposed toward coating 262 function as spreading components. Outputlight sources similar to bundle 290 could also be used in theconfigurations shown in FIGS. 14-16.

FIGS. 20-22 illustrate a configuration in which multiple divergent beamsare received from different output light sources such as LEDs or opticalfibers, positioned at a distance from coating 262 in order to illuminatethe entire area of photosensor array 260 in the y-direction. In FIG. 20,the sources are shown from the side, represented by aligned source 300,while in FIG. 21, each individual source is shown separately, as sources302, 304, and 306. Sources 302, 304, and 306 could each be point-like,or stripe-like LEDs or linear fiber bundles. A configuration similar tothat in FIGS. 20-22 could also be used with broad area sources. Sources302, 304, and 306 can then indicate subareas of the broad area sourcethat can be analyzed independently; for example, subareas can beanalyzed to measure photon energy homogeneity over the broad area.

Lens 310 in FIGS. 20 and 21 represents any appropriate positiveanamorphic lens or lens group, and is illustratively shown as apiano-convex cylindrical lens. As a result, lens 310 focuses each beamin the x-direction, as shown in FIG. 21, while permitting each beam tocontinue to spread in the y-direction, as shown in FIG. 20, resulting inmultiple spots or stripes 312 as shown in FIG. 22. As in FIG. 15,spreading of output light in the y-direction occurs in the two distancesor gaps before and after lens 310, because air, gas, a transparentmedium, or vacuum in the gaps functions as a spreading component. If thestripes are adequately resolved in the x-direction, this configurationavoids cross-talk between different output light sources. As in FIGS.17-19, coating 262 has a gradient in the y-direction, but is homogeneousin the x-direction, but could alternatively be inhomogeneous in thex-direction as discussed above.

FIGS. 23 and 24 illustrate another configuration that would producemultiple spots or stripes as illustrated in FIG. 22. In thisimplementation, the optical components include both imaging lens 320 andany appropriate negative anamorphic lens or lens group, illustrativelyshown as a piano-concave cylindrical lens 322, while other componentsare the same as in FIGS. 19-21. The lenses 320 and 322 image the outputlight beams in the x-direction to avoid cross-talk between beams, butallow each beam to remain spreaded over the whole width of array 260 inthe y-direction, due to the effect of lens 322. Due to this specialconfiguration, the light is substantially parallel in the y-directionenabling higher wavelength resolution. In this configuration, spreadingof output light occurs in the distance or gap between sources 302, 304,and 306 and lens 320, because air, gas, a transparent medium, or vacuumin the gap functions as a spreading component. A configuration similarto that in FIGS. 23 and 24 could be implemented with a Selfoc® lensarray instead of imaging lens 320. Also, a configuration similar to thatin FIGS. 23 and 24 could also be used with broad area sources asdiscussed above.

FIGS. 25-27 illustrate yet another example in which multiple point-likeor stripe-like light sources such as LEDs or linear fiber bundlesprovide output light beams. In the view in FIG. 25, all of the sourcesare aligned, represented by aligned source 330, while each source 332,334, 336, and 338 is shown individually in FIG. 26. Rather than lensesor lens-like optical components as in FIGS. 20-24, this configurationincludes blades 340, which could be reflecting blades, and which preventcross-talk between different beams. As a result, a pattern of multiplespots or stripes 342 is produced, as shown in FIG. 27. In thisconfiguration, spreading of output light occurs in the distance or gapbetween each of sources 332, 334, 336, and 338 and coating 262, becauseair, gas, a transparent medium, or vacuum in each gap functions as aspreading component. In other respects, this implementation is similarto those of FIGS. 20-24.

Various other techniques could be used to provide output light from astimulus-wavelength converter to an implementation of assembly 34. Thetechniques described in relation to FIGS. 12-27 are merely illustrative,and could be varied in many ways.

FIG. 28 illustrates exemplary operations in producing apparatus likedevice 10 in FIG. 1. In particular, the operations in FIG. 28 make itpossible to produce a device in which output light from astimulus-wavelength converter is incident on readout components thatinclude a light sensing assembly and one or more spreading components.

The operation in box 400 in FIG. 28 produces a stimulus-wavelengthconverter of any of the types described above. For example, theoperation in box 400 could produce a fiber-optic sensor with FBGs, a POFsensor, a photonic crystal sensor, an optical biosensor, etc.

The operation in box 402 then produces a device with the converter frombox 400, a light sensing assembly, and one or more spreading components,configured so that output light from the converter is incident on thelight sensing assembly, such as in one of the ways described above inrelation to FIGS. 12-27. This operation can be performed in anyappropriate way, including butt-coupling as in FIGS. 12, 17, and 18 orwith spaced components as in FIGS. 14, 15, 20, 21, and 23-26.

FIG. 29 illustrates features of a system that includes one or moredevices as in FIG. 1. In FIG. 29, system 600 is an exemplary system thatcould be used to obtain wavelength information from light output fromstimulus-wavelength converters as described above. System 600illustratively includes central processing unit (CPU) 602 connected tovarious components through bus 604, but a wide variety of otherarchitectures could be employed, including any appropriate combinationof hardware and software, as well as specialized hardware componentssuch as application specific integrated circuits (ASICs) for one or moreof the illustrated components or in place of a software componentexecuted by CPU 602.

System 600 also includes external input/output (I/O) component 606 andmemory 608, both connected to bus 604. External I/O 606 permits CPU 602to communicate with devices outside of system 600. For interactiveapplications, external I/O 606 could be connected to a suitable userinterface, such as a monitor and keyboard (not shown). Additionalcomponents connected to bus 604 are within or connected to system 600.In the illustrated implementation of system 600, IC I/O 610 is acomponent that permits CPU 602 to communicate with one or more ICs insensing assembly 22. M ICs are illustrated by a series from IC(O) 612 toIC(M−1) 614, including IC(m) 616 with a photosensor array 618.

Memory 608 illustratively includes program memory 630, althoughinstructions for execution by CPU 602 could be provided in any of theways described above. The routines stored in program memory 630illustratively include readout and compare routine 640. In addition,program memory 630 could store various additional subroutines (notshown) that CPU 602 could call in executing routine 640.

In executing routine 640, CPU 602 can provide signals to each of ICs 612through 614 to read out subrange cells and to compare the photosensedquantities to obtain wavelength information such as differentialquantities. Before comparison, routine 640 can also optionally read outreference cells and use their photosensed quantities to adjustphotosensed quantities from subrange cells, such as with techniquesdescribed in co-pending U.S. patent application Ser. No. 11/______[Attorney Docket No. 20040195Q-US-NP/U1047/024], entitled “PhotosensingThroughout Energy Range and in Subranges” and incorporated herein byreference.

Routine 640 can perform comparison in several ways, depending on thetype of wavelength information being obtained. To obtain wavelengthshift information, photosensed quantities from two cells or two sets ofcells can be compared similarly to the technique illustrated in FIG. 2;with appropriate differential amplifier circuitry on an IC, routine 640may be able to perform the comparison with especially high resolution bycontrolling readout from the cells to the differential amplifier, afterwhich the analog comparison result can be converted to a digital valuefor transfer through bus 604 to CPU 602. A differential amplifier canalso be used for an especially high resolution comparison of intensitiesof two different currents of a position sensor. Rather than adifferential amplifier, any other suitable analog component could beused that provides a biased or unbiased analog difference or analogratio.

Photosensed quantities could instead be digitized before comparison, inwhich case CPU 602 could perform any appropriate routine to obtain adigital differential quantity or any other data indicating a comparisonresult. Such a routine could also include normalizing or otherwiseadjusting each digitized value prior to comparison. The routine couldperform subtraction, division, or any other operation that produces aresult indicating the difference between two photosensed quantities.

Although digital comparison is not likely to be as precise as highresolution analog comparison, it may allow greater flexibility. Forexample, rather than simply performing pairwise comparison, CPU 602could divide all the non-zero or above-threshold photosensed quantitiesinto two groups in any appropriate way, add the quantities to obtain asummed quantity for each group, and then compare the summed quantities,possibly after weighting for difference in the number in each group. Thegroups could be chosen based on position or any other suitablecriterion.

More generally, to increase resolution, CPU 602 can compare photosensedquantities with calibration values. The term “calibration value” is usedherein to refer to any value obtained by a measurement that eitherestablishes a standard or is based on a previously established standard.A calibration value could, for example, indicate how to categorize,weight, or otherwise interpret, adjust, or correct a given measuredvalue such as a photosensed quantity or photosensed position. Onceobtained, a calibration value is typically saved in an appropriate formfor subsequent comparison with measured values. Where a calibrationvalue indicates a quantity of photons, it may be referred to as a“calibration quantity”.

Absolute wavelength resolution is important to quantify the absolutevalue of a stimulus (e.g. the actual temperature), while relativewavelength resolution is important to quantify the change in a stimulus(e.g. the size of a temperature change). Both types of informationrequire calibration to obtain calibration values for later comparison.It should be noted, however, that absolute wavelength calibration canchange more easily than relative wavelength calibration as a result ofsmall changes in the setup (e.g. non-collimated light input), so thatrelative wavelength resolution is more robust.

During calibration, the readout components are illuminated with a knownlight source and the response is stored in an appropriate calibrationdata structure. Exemplary calibration techniques are described inco-pending U.S. patent application Ser. No. 10/922,870, entitled“Chip-size Wavelength Detector” and incorporated herein by reference inits entirety.

For absolute wavelength information, a calibration data structure canindicate correspondences between positions and wavelengths; for relativewavelength information, a calibration data structure can indicatecorrespondences between position differences or relative photosensedquantities, on the one hand, and wavelength, peak value, distribution,or stimulus value differences on the other. Routine 640 can comparequantities it reads out with one or more calibration data structures toobtain either or both of these types of information.

Wavelength information obtained by routine 640 can be combined in anappropriate data structure (not shown), such as by forming a data arrayor list. After wavelength information has been obtained, CPU 602 can usethe raw wavelength information, for example, to calculate or obtain froma calibration data structure a corresponding value for the stimulus orfor a stimulus change (e.g. temperature, pressure, presence or absenceof analyte, etc.). CPU 602 can provide the wavelength information orcorresponding values through external I/O 606. For example, all of thewavelength information or corresponding values could be combined into asingle data structure and provided through external I/O 606 through asuitable streaming operation.

In general, system 600 could be implemented with any devices thatinclude stimulus-wavelength converters. Furthermore, system 600 could beimplemented for many applications, some of which are illustrated below.

FIG. 30 shows camera 700, an example of apparatus that includes one ormore devices as in FIG. 1. Camera 700 receives output light from astimulus-wavelength converter, represented in FIG. 30 by point-likesource 702.

Output light from source 702 is spreaded as it propagates across the gapto imaging lens 710, and then is directed in a collimated fashion ontoan assembly that includes a laterally varying transmission structuresuch as coating 712 and also a photosensor component such as IC 714.Collimation can avoid error arising if coating 712 were laterallyinhomogeneous due to dependence on incidence angle at its entry surface.Processing system 720 then obtains readout signals from IC 714 and usesthe readout signals to obtain wavelength information.

A camera with general features as shown in FIG. 30 has been implementedby modifying an inexpensive commercially available Webcam-type camerawith a cylindrical lens and a CCD array. A linear variable filter wasplaced over the CCD array, such as a GaAs/AlAs graded Fabry-Perot cavityproduced similarly to the technique in FIG. 8 or a commerciallyavailable filter available from JDS Uniphase. The camera was thenpositioned to receive light from a wavelength tunable light source, suchas a tunable VCSEL from ULM-Photonics, which was controlled to providespots of light at several different wavelengths including 942.81 nm,943.08 nm, 943.45 nm, 943.92 nm, 944.55 nm, and 945.37 nm. For eachwavelength, signals read out from the array were converted into an imagein the conventional manner, from which positions of maximum photonquantity could be visually obtained.

FIG. 31 summarizes the positions obtained visually as described abovefor the wavelengths listed above, with the horizontal axis representingwavelength in nm and with the vertical axis representing position on thearray in arbitrary units, specifically numbers of cells in the array.For each wavelength, the position value was visually obtained, and curve730 connects the position values of spots for the above-listedwavelengths. As can be seen, wavelengths were successfully resolved thatdiffered by less than 0.1 nm.

FIG. 32 shows a test implementation similar to techniques described inco-pending U.S. patent application Ser. No. 10/922,870, entitled“Chip-size Wavelength Detector” and incorporated herein by reference inits entirety. Device 750 includes a three-terminal semiconductorposition sensor that responds to an incident light spot by providing asignal indicating the light spot's position on the upper surface of thesensor. The sensor includes n-type silicon substrate 752 with tworesistive layers separated by a p-n junction. On the upper side is anion implanted p-type resistive layer 754 with two contacts or electrodes756 and 758 at opposite ends. On the lower side is an ion implantedn-type resistive layer 760, serving as the device's bias electrode 762.

Over the upper surface of substrate 752 is laterally varyingtransmission structure 770, which can be implemented in any of the waysdescribed above in relation to FIGS. 4-11 but has been experimentallyimplemented with a structure like that in FIG. 4, designed to transmitwavelengths in part of the spectral range where silicon photon detectorsare sensitive. When light source 772 illuminates structure 770 with asingle wavelength within this spectral range at which structure 770 istransmissive, structure 770 provides a spot at the wavelength'scorresponding position 774 to the upper surface of substrate 752, andphotocurrent flows from point 774 through resistive layers 754 and 760to electrodes 756 and 758. The currents from electrodes 756 and 758 canbe provided to a differential amplifier as described above or convertedto digital values and compared to obtain a signal indicating thelocation of position 774.

Any other suitable spreading, separating, and propagation techniquescould be used in the setups shown in FIGS. 30 and 32, including any ofthose described above in relation to FIGS. 12-27. Position sensors likethat shown in FIG. 32 and other position sensor arrays and devices ingeneral can be used with any of the techniques in FIGS. 12-27.

The graph in FIG. 33 shows that the test implementation in FIG. 32 canperform extremely high, sub-picometer wavelength resolution. In thisimplementation, light source 772 was a tunable 950 nm VCSEL. Thedifferential signal across electrodes 756 and 758 is shown as a functionof time during a session in which the illumination wavelength of theVCSEL was adjusted by increments and decrements (Δλ) of approximately0.1, 0.2, and 0.5 pm. Each increment and decrement produced a detectablenearly instantaneous excursion of the differential signal, appearing inFIG. 33 as nearly vertical segments of the curve.

The graph in FIG. 34 was obtained with a modified version of the testimplementation in FIG. 32. In this version, light source 772 was aspectrally filtered halogen lamp that provides monochromatic light withFWHM of about 1 nm, and with the capability of sweeping the wavelengthover a large wavelength range. For curve 800, structure 770 had awavelength-to-distance gradient of 32 nm/mm, and for curve 802, agradient of 4 nm/mm. In curve 800, the differential signal changesmonotonically over a range of 100 nm with a slope of approximately 86mV/nm. In curve 802, the differential signal changes similarly, but witha much greater slope. This illustrates an example in which decreasingthe gradient improves wavelength resolution but sacrifices wavelengthrange, while increasing the gradient enables large wavelength rangecoverage at a lower wavelength resolution.

The graph in FIG. 35 was obtained by modifying the setup for FIG. 34,replacing the position sensor with a photosensor array and connectingthree consecutive cells in a row of the array to two differentialamplifiers, with one differential amplifier comparing the first andsecond cells and with the other comparing the second and third cells.Curve 810 results from comparing the first and second cells, and curve812 from comparing the second and third cells. In both curves, thedifferential signal changes with wavelength, but the two pairs of cellsaddress different wavelength ranges.

FIG. 36 shows another test implementation in a temperature sensingdevice 850. Device 850 includes FBG sensor 852, an 834 nm FBG mounted atone side on a cooling/heating element that is connected to a temperaturecontroller such that temperature can be tuned by adjusting aheating/cooling current; the other side of sensor 852 was, however,exposed to ambient air, so that temperature control was imperfect. Lightsource 854 is a super luminescent emitting diode (SLED) that provideslight in a narrow band around 817 nm to sensor 852 through fiber 856 andcoupler 858, which can be a commercially available 3 dB 2×1 coupler.

Reflected light from sensor 852, with its wavelength indicatinginformation about temperature, returns through coupler 858 and fiber 860to laterally variable transmission structure 862, implemented in one ofthe ways described above in relation to FIGS. 4-11 and having a gradientof 32 nm/mm. A spot of light corresponding to the reflected wavelengthis provided to photodiode array 864. Two cells of array 864 arepositioned to receive two wavelength subranges, and their outputcurrents I₁ and I₂ are provided to differential amplifier 866 forcomparison.

The differential signal from amplifier 866 has a magnitude indicatingthe reflected wavelength from sensor 852, as shown in FIG. 37. Curve 880indicates the resistance of a temperature monitoring thermistorintegrated into the cooling/heating element as a function of time duringa session, where the controller changes the temperature of thecooling/heating element from one to another set value. Curve 882indicates the differential signal from amplifier 866 as a function oftime during the same session. As can be seen, curve 882 follows curve880 in general and especially during transients. The differences duringsteady state might result from the effect of ambient air on sensor 852,providing noise that caused its temperature to fluctuate when theresistance was relatively stable.

FIG. 38 shows steady state differential signal as a function oftemperature for device 750 in FIG. 36, with the circles indicatingmeasurements for temperatures across a wide temperature range. As can beseen, a linear fit produces the curve y=229-12.2×, so that thesensitivity is approximately 12.2 mV/° C. This sensitivity allowstemperature resolution down to 0.1° C.

FIG. 39 shows device 900, which includes 96-well plate 902 and readoutcomponents 904. FIG. 39 shows only parts of well plate 902 and readoutcomponents 904, with features relating to one well. Well plate 902 canbe used, for example, with equipment that injects a sample of fluid intoeach well for analysis.

Well plate 902 can be implemented with a BIND Biosensor™ from SRUBiosystems, Woburn, Mass., which functions as an 8×12 array ofstimulus-wavelength sensors. In other words, each well 912 is surroundedby walls 914 that function to separate contents of wells and preventcontamination, and walls 914 together form a stable lattice-likeframework or structure on one side of which foil grating 916 is mounted.The fluid or other contents of well 912 modify the reflected wavelengthof the well's region of grating 916. The well's region of grating 916therefore includes a “grating component”, meaning an optical sensor oroptical sensing component that, when illuminated with collimatedbroadband light, is designed to reflect only a narrow band ofwavelengths that depends on the fluid or other contents of well 912.Additional features of well plate 902 are described in U.S. PatentApplication Publication Nos. 2003/0077660 and 2004/0223881 and inCunningham et al., Journal of Biomolecular Screening, 9(6), 2004, p.481, all of which are incorporated herein by reference.

Readout components 904 for each well include collimating lens 920, whichreceives broadband light through illuminating fiber 922, contained inoptical fiber probe 924 with readout fiber 926; each well could bemeasured by more than one probe 924. Readout fiber 926 transmitsreflected light from a well's region of foil grating 916 to light sensorassembly 930, which can be implemented in any of the ways describedabove. Readout components 904 can include similar components for eachwell in the array, and a single light sensor assembly 930 can receivereflected output light in parallel from a fiber bundle that includes thereadout fibers 926 for an 8-well row of the array or possibly even atwo-dimensional fiber array that covers all 96 wells.

Spreading components and other propagation components for the fiberbundle can be configured in one of the ways described above or asdescribed in U.S. Patent Application Publication Nos. 2003/0077660 and2004/0223881. All the light sensor assemblies 930 for the array can beconnected in parallel to circuitry for obtaining wavelength informationas described above.

In general, any of the lenses described in relation to FIGS. 1-39 can beimplemented or replaced by any suitable type of refractive ordiffractive optics, including but not limited to spherical lenses,Selfoc® lenses, and gradient index (GRIN) lenses. Also, any lensdescribed in these examples might be replaced by a lens with similarfunctionality, e.g. a plano-concave lens might be replaced by abi-concave lens or any other appropriate negative anamorphic lens orlens group, a plano-convex lens might be replaced by a biconcave lens orany other appropriate positive anamorphic lens or lens group, and soforth.

Some of the implementations of FIGS. 1-39 illustrate examples ofapparatus that include a stimulus-wavelength converter, a transmissionstructure, and a spreading component. The stimulus-wavelength converterprovides output light in response to one or more stimuli. Thetransmission structure has an entry surface at which it receives theoutput light and an exit surface; the entry surface extends in a firstdirection and the transmission structure's energy transmission functionvaries laterally in the first direction. The spreading component spreadsthe output light from the converter across the entry surface in at leasta spreading direction that is not perpendicular to the first direction.

In specific implementations, the converter can provide the output lightwithin a range of photon energies; in response to spreaded light withenergies in a given subrange, the transmission structure can provideoutput photons at a respective position of the exit surface. Also, theconverter can provide output light from a fiber end facet, from apoint-like source, or from a broad area source. The converter caninclude a set of optical fibers that each respond to a respectivestimulus and provide output light to the spreading component. Thespreading direction can be approximately the same as the firstdirection.

Also, in specific implementations, at least one of the optical fiberscan provide light output through an end positioned in a buttingrelationship adjacent the entry surface, and the spreading component caninclude a surface at the end. At least one of the fibers can providelight output through an end, and the spreading component can bepositioned between the end and the entry surface, such as air, gas, atransparent medium, or vacuum in a gap or part of a Selfoc® or GRINlens. With two or more optical fibers, the system can also include aseparation component that keeps light output from the fibers separate,such as a lens that collimates, images, or focuses or blades. If thefiber ends are aligned in a second direction perpendicular to the firstdirection, the spreading direction can be approximately the same as thefirst direction.

In further specific implementations, the apparatus can also includephotosensing components that photosense output photons from the exitsurface at a set of positions along the first direction. Where theoutput light includes wavelength information, a system that includes theapparatus can also include circuitry that responds to the photosensingcomponents, providing signals indicating the wavelength information; thecircuitry can include a processor.

Implementations in FIGS. 1-39 further illustrate examples of a sensingmethod that includes receiving output light from a stimulus-wavelengthconverter that provides the output light in response to one or morestimuli. The method spreads the output light in at least a spreadingdirection across a transmission structure's entry surface. In responseto the spreaded light, the method provides output photons at the exitsurface in accordance with an energy transmission function that varieslaterally in a first direction in which the entry surface extends. Thefirst direction and the spreading direction are not perpendicular toeach other.

In specific implementations, the output light is provided as describedabove. The method can also, with one or more photosensing components,photosense the output photons at a set of positions along the firstdirection. If the output light from the converter includes wavelengthinformation, signals indicating the wavelength information can beprovided in response to photosensing results.

Some of the implementations in FIGS. 1-39 also illustrate examples ofapparatus that includes two or more sources that provide light, atransmission structure as described above, and a propagation component.The propagation component spreads light from each source across thetransmission structure's entry surface and keeps the light from thesources separate. The propagation component spreads the light in atleast a spreading direction that is not perpendicular to the firstdirection of the transmission structure.

In specific implementations, the fiber ends are aligned in a seconddirection approximately perpendicular to the first direction, and thespreading direction can be approximately the same as the firstdirection. The apparatus can also include one or morestimulus-wavelength converters that provide output light through thesources. Each of the sources can be a fiber end facet, a point-likesource, or a broad area source. Each can be an optical fiber endpositioned in a butting relationship adjacent the entry surface, and thepropagation component can include an optical fiber surface at each end.The propagation component can be positioned between the sources and theentry surface, such as air, gas, a transparent medium, or vacuum in agap; one or more lenses; or a set of blades.

In general, many additional techniques could be employed in theimplementations of FIGS. 1-39, such as adjusting photosensed quantitiesfrom subrange cells based on photosensed quantities from referencecells, as described in greater detail in co-pending U.S. patentapplication Ser. No. 11/______ [Attorney Docket No.20040195Q-US-NP/U1047/024], entitled “Photosensing Throughout EnergyRange and in Subranges” and incorporated herein by reference. Thisadjustment could be performed on analog quantities or, after conversionto digital values, on digital quantities.

The implementations in FIGS. 1-39 illustrate various applications oftechniques as described above, including readout fromstimulus-wavelength converters and other optical sensors; use in acamera or other imaging device; use in temperature measurement; and usein readout of a well plate. Sensing techniques involving laterallyvarying transmission of light as a function of photon energy, asexemplified by the implementations in FIGS. 1-39, can also be applied inmany other applications. A particularly interesting application ofoptical sensor readout is in automobiles, where optical sensorrobustness against EMI is especially valuable. Other applicationsinvolve biological, chemical, and environmental sensors.

Various of the techniques described above have been successfullyimplemented or simulated, including the production of a detector thatincludes a commercially available IC covered with a laterally gradedFabry-Perot cavity filter on a glass slide. Wavelength resolution hasbeen experimentally determined and successfully simulated on a computer.Anti-resonant waveguide techniques have been successfully tested. Asdescribed above, temperature measurement has been successfully performedby using a commercially available detector coated with a laterallyvarying Fabry-Perot coating.

The exemplary implementations described above are advantageous becausethey can provide compact, inexpensive components to perform functionssuch as readout of stimulus-wavelength converters or other opticalsensors. In general, the techniques can be implemented in existingsensors, photosensors, and cameras, including camcorders, digicams, andwebcams available in the consumer market. The results of photosensingcan be read out and compared rapidly.

Readout implementations as described above can be applied in variousapplications, several of which are described or mentioned above. Readoutimplementations as described above can also be applied in smart sensors,in sensors with bus capabilities, and in sensors with self-diagnosticcapabilities, with self-calibration, and with self-adaptation.

The exemplary implementations described above generally rely ontransmission structures that include highly reflective interfaces, sothat much of the incident light is reflected and only a small fractionreaches the photosensor array. Therefore, the techniques described aboveare especially useful in applications in which light intensity is veryhigh or a light source emits through a large area or over an extendedtime. In addition, the above techniques make it possible to increasesensitivity by choosing very long integration times (without loss ofthroughput capacity), simpler optics, and no dispersion element. Bycontrast, some conventional systems such as monochromators lose alllight defracted into the 0^(th), 2^(nd), and higher orders. In theimplementations described above, very high light yield can be achievedby combining a transmission structure with a highly sensitivephotosensor array, such as one that includes avalanche photodetectors.

In addition, components could have various shapes, dimensions, or othernumerical or qualitative characteristics other than those illustratedand described above. For example, in the exemplary implementationsdescribed above, cells of a photosensor array photosense in differentsubranges of an application's photon energy range. The subranges ofcells could have any appropriate widths and relationships, and could,for example, overlap or be distinct. The width of a cell's subrange canbe chosen by designing the transmission structure and the cell sensingarea; for example, the width may be as small as 0.1 nm or as great astens of nanometers.

In the above exemplary implementations, each transmission structure'senergy transmission function generally varies in a straight linedirection, and each spreading component generally spreads light in thesame straight line direction. It would be possible, however, to have atransmission function and spreading that occur in different,non-perpendicular directions and in directions that are not straight butrather are curved or angled.

Some of the above exemplary implementations involve specific materials,such as in photosensor arrays or position sensors and transmissionstructures, but the invention could be implemented with a wide varietyof materials and with layered structures with various combinations ofsublayers. In particular, photosensor arrays for a desired speed,sensitivity and wavelength range could have any suitable material, suchas silicon, germanium, indium-gallium-arsenide, gallium arsenide,gallium nitride, or lead sulphide, and could be produced with anyappropriate kind of devices, including, for example, photodiodes,avalanche photodiodes, p-i-n diodes, photoconductors, and so forth, withany appropriate technique for sensing and reading out informationwhether based on CCD, CMOS, or other techniques. Various commerciallyavailable detector arrays have pixel densities as high as tenmegapixels, and some high density ICs have become relativelyinexpensive.

Similarly, transmission structures could be fabricated with anyappropriate techniques, including thin film technology such assputtering, e-beam or thermal evaporation with or without plasmaassistance, epitaxial growth, MBE, MOCVD, and so forth. To produce Braggmirrors, appropriate pairs of materials with low absorption coefficientsand large difference in refractive indices could be chosen, bearing inmind the photon energies of interest; exemplary materials includeSiO₂/TiO₂, SiO₂/Ta₂O₅, GaAs/AlAs, and GaAs/AlGaAs. Thicknesses of layerin transmission structures may vary from 30 nm up to a few hundrednanometers.

Some of the above exemplary implementations involve particular types oftransmission structures, such as Bragg mirrors and paired distributedBragg reflectors separated by a Fabry-Perot cavity, but thesetransmission structures are merely exemplary, and any transmissionstructure that has laterally varying optical thickness could be used.Various techniques could be used to produce transmission structures withlateral variation in addition to those described above, including,during deposition, tilting the substrate, using a shadow mask, or usinga temperature gradient to obtain graded layer thickness; also, duringhomogeneous deposition, off-axis doping, such as by e-beam, MBE, orMOVPE, could produce lateral variation.

Some of the above exemplary implementations employ enhanced light-targetinteraction to obtain fluorescence. In general, however, the techniquesdescribed above could also be used for light from self-emitting orauto-fluorescing objects such as particles. Furthermore, various typesof fluorescence, photo-luminescence, chemo-fluorescence, inelasticscattering, and so forth could be employed. The technique ofanti-resonant waveguiding, described above, is only one of manytechniques that could be used for enhanced light-target interaction, andany such excitation technique could be applied continuously orintermittently along a path. Various parameters could be adjusted toobtain anti-resonant waveguiding, including the shape of quartz or glasssurrounding the channel; a thinner structure is generally better, with asurface parallel to the channel generally being required.

Additional description of excitation techniques is found in co-pendingU.S. patent application Ser. No. 11/______ [Attorney Docket No.20051553-US-NP/U1047/027], entitled “Providing Light to Channels orPortions” and incorporated herein by reference in its entirety.

Some of the above exemplary implementations use specificstimulus-wavelength converters or other optical sensors or specificpropagation components to obtain light with desired characteristics, butvarious other converting or sensing techniques and propagationcomponents could be used within the scope of the invention. Morespecifically, some of the exemplary implementations include spreadingcomponents or separation components of specific types, but various otherspreading components or separation components could be used within thescope of the invention. Some of the exemplary implementations show aspecific number of aligned light sources, but the techniques could beused with any suitable number of light sources, and the light sourcescould be arranged in any appropriate way.

The exemplary implementation in FIG. 29 employs a CPU, which could be amicroprocessor or any other appropriate component. Furthermore, as notedabove, the adjustment of photosensed quantities could be done eitherdigitally or with analog signals, and could be done either on the sameIC as the photosensor array, on other components, or on a combination ofthe two, with any appropriate combination of software or hardware.

The above exemplary implementations generally involve production and useof ICs, transmission structures, stimulus-wavelength conversiontechniques, propagation components, spreading components, separatingcomponents, and readout and comparing circuitry following particularoperations, but different operations could be performed, the order ofthe operations could be modified, and additional operations could beadded within the scope of the invention. For example, in implementationsin which a transmission structure is on a separate substrate from aphotosensor array, the transmission structure could be moved relative tothe photosensor array between consecutive sensing operations. Also,readout of adjusted or unadjusted sensed quantities from an IC could beperformed serially or in parallel, and could be performed cell-by-cellor in a streaming operation.

While the invention has been described in conjunction with specificexemplary implementations, it is evident to those skilled in the artthat many alternatives, modifications, and variations will be apparentin light of the foregoing description. Accordingly, the invention isintended to embrace all other such alternatives, modifications, andvariations that fall within the spirit and scope of the appended claims.

1. Apparatus comprising: a stimulus-wavelength converter that providesoutput light in response to one or more stimuli; a transmissionstructure that has an entry surface at which it receives the outputlight from the converter and an exit surface; the entry surfaceextending in a first direction in which the transmission structure has alaterally varying energy transmission function; and a spreadingcomponent that spreads the output light from the converter across thetransmission structure's entry surface in at least a spreading directionthat is not perpendicular to the first direction.
 2. The apparatus ofclaim 1 in which the converter provides the output light within a rangeof photon energies; in response to spreaded output light received at theentry surface with energies in a given subrange of the range ofenergies, the transmission structure providing output photons at arespective position of the exit surface.
 3. The apparatus of claim 1 inwhich the spreading direction is approximately the same as the firstdirection.
 4. The apparatus of claim 1 in which the stimulus-wavelengthconverter includes a set of one or more optical fibers that each respondto a respective stimulus and provide output light to the spreadingcomponent
 5. The apparatus of claim 4 in which at least one of the setof optical fibers provides light output through an end positioned in abutting relationship adjacent the entry surface of the transmissionstructure; the spreading component including a surface at the end. 6.The apparatus of claim 4 in which at least one of the set of opticalfibers provides light output through an end; the spreading componentbeing positioned between the end and the entry surface of thetransmission structure.
 7. The apparatus of claim 6 in which the end andthe entry surface are separated by a gap; the spreading componentincluding at least one of air, gas, a transparent medium, or vacuum inthe gap.
 8. The apparatus of claim 6 in which the spreading componentincludes at least part of a lens between the end and the entry surface.9. The apparatus of claim 8 in which the lens is a Selfoc® or gradientindex lens.
 10. The apparatus of claim 4 in which the set of opticalfibers includes two or more optical fibers, each having an end throughwhich it provides respective light output; the system furthercomprising: a separation component that keeps light output from theoptical fibers separate.
 11. The apparatus of claim 10 in which theseparation component includes blades or includes at least one lens thatcollimates, images, or focuses.
 12. The apparatus of claim 11 in whichthe separation component includes a positive anamorphic lens or lensgroup or includes a focusing lens and a negative anamorphic lens or lensgroup between the focusing lens and the entry surface of thetransmission structure.
 13. The apparatus of claim 12 in which thefocusing lens is a Selfoc® or gradient index lens.
 14. The apparatus ofclaim 10 in which the ends of the optical fibers are aligned in a seconddirection approximately perpendicular to the first direction; thespreading direction being approximately the same as the first direction.15. The apparatus of claim 1 in which the stimulus-wavelength converterprovides output light from a fiber end facet, from a point-like source,or from a broad area source.
 16. The apparatus of claim 1, furthercomprising: one or more photosensing components that photosense outputphotons from the transmission structure's exit surface at a set ofpositions along the first direction.
 17. The apparatus of claim 16 inwhich the photosensing components include at least one of a photosensorarray, a position sensor, and a position sensor array.
 18. A system thatincludes the apparatus of claim 16; the output light from the converterincluding wavelength information; the system further comprising:circuitry that responds to the photosensing components, providingsignals indicating the wavelength information.
 19. The system of claim18 in which the circuitry includes a processor.
 20. A sensing methodcomprising: receiving output light from a stimulus-wavelength converter,the converter providing the output light in response to one or morestimuli; spreading the output light received from the converter in atleast a spreading direction across a transmission structure's entrysurface; in response to the light spreaded across the entry surface,providing output photons at an exit surface of the transmissionstructure in accordance with an energy transmission function that varieslaterally in a first direction in which the entry surface extends, thefirst direction and the spreading direction not being perpendicular toeach other.
 21. The method of claim 20 in which the output light fromthe stimulus-wavelength converter is provided through a set of opticalfiber ends; the act of spreading the output light comprising at leastone of: propagating the output light through surfaces at the opticalfiber ends; propagating the output light through at least one of air,gas, a transparent medium, or vacuum; and propagating the output lightthrough a lens.
 22. The method of claim 20, further comprising: with oneor more photosensing components, photosensing the output photons fromthe exit surface at a set of positions along the first direction. 23.The method of claim 22 in which the output light from the converterincludes wavelength information, the method further comprising: inresponse to photosensing results from the photosensor components,providing signals indicating the wavelength information.
 24. Apparatuscomprising: two or more sources that provide light that includeswavelength information; a transmission structure that has an entrysurface at which it receives light and an exit surface, the entrysurface extending in a first direction in which the transmissionstructure has a laterally varying energy transmission function; and apropagation component that spreads the light from each source across thetransmission structure's entry surface and keeps the light from thesources separate; the propagation component spreading the light in atleast a spreading direction that is not perpendicular to the firstdirection.
 25. The apparatus of claim 24 in which the light sources arealigned in a second direction approximately perpendicular to the firstdirection; the spreading direction being approximately the same as thefirst direction.
 26. The apparatus of claim 24, further comprising: oneor more stimulus-wavelength converters that provide output light throughthe sources.
 27. The apparatus of claim 24 in which each of the lightsources is a fiber end facet, a point-like source, or a broad areasource.
 28. The apparatus of claim 24 in which each of the light sourcesis an optical fiber end positioned in a butting relationship adjacentthe entry surface of the transmission structure; the propagationcomponent including an optical fiber surface at each end.
 29. Theapparatus of claim 24 in which the propagation component is positionedbetween the sources and the entry surface of the transmission structure.30. The apparatus of claim 29 in which the sources and the entry surfaceare separated by a gap; the propagation component including at least oneof: air, gas, a transparent medium, or vacuum in the gap; one or morelenses; and a set of blades.
 31. The apparatus of claim 30 in which thepropagation component includes at least one lens that collimates,images, or focuses.
 32. The apparatus of claim 31 in which theseparation component includes a positive anamorphic lens or lens groupor includes a focusing lens and a negative anamorphic lens or lens groupbetween the focusing lens and the entry surface of the transmissionstructure.